With the same version I get the same error.
Trace file shows:
ORA-07445: exception encountered: core dump [ACCESS_VIOLATION] [_qknviAllocate+15] [PC:0x21E1FFB] [ADDR:0x0] [UNABLE_TO_READ] []
which denotes an Oracle bug.

Hopefully, I got that right. I think this is more the typical traverse the tree forward and backward. This would give me one denormalized "view"
of all my hierarchical data into one place. I could traverse any and all data this way.

I'll try to give this a go based upon the data above and your excellent code example.

likewise for all the 21 tablelist in the child column the insert statement should be generated and executed and id_xref_tbl is a cross refencence table where the id value from all the table should be populated table having columns ID_VALUE and OBJECT_NAME

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